Structural Screws
Structural screws are engineered fasteners designed to replace or outperform lag screws, carriage bolts, and common framing nails in many wood-to-wood structural connections.
Fast Facts
- What Is It?
- A high-strength, code-evaluated screw for structural wood connections.
- Common Uses
- Ledger fastening, beam-to-post connections, multi-ply beam assembly, deck framing, and engineered hardware installation.
- Cost Range
- $0.35–$2.50 each depending on diameter, length, coating, and brand.
- Durability
- Excellent when the coating or stainless grade matches the exposure and preservative chemistry.
Specifications
| Property | Value |
|---|---|
| Common Brands | Simpson Strong-Drive SDS / SDWS, GRK RSS, FastenMaster LedgerLOK / HeadLOK |
| Evaluation | ICC-ES or equivalent third-party evaluation report required for code substitution |
| Typical Diameters | 0.195" to 0.276" |
| Typical Lengths | 3" to 12" |
| Installation | Driven with impact driver or high-torque drill; pilot holes depend on manufacturer |
| Corrosion Requirement | Use approved coating or stainless steel in ACQ / exterior exposure |
What Structural Screws Do Better Than Commodity Screws
Structural screws are purpose-built connectors with higher tensile, shear, and withdrawal capacity than standard wood screws. They are engineered as part of a load path, not merely as a convenience fastener.
For contractors, the main advantage is speed: no lag screw predrilling in many cases, no wrenching, and easier installation in tight framing conditions. That labor savings is why structural screws are now common in deck ledgers, beam plies, and heavy framing connectors.
Where Code Approval Matters
A structural screw only counts as structural when it is installed exactly as tested. Diameter, embedment, spacing, edge distance, and coating all affect the published capacity. Always verify the evaluation report and manufacturer chart before substituting it for a lag screw or bolt.
This is especially important in engineered or inspected work. A building official may accept a structural screw substitution, but only if the product documentation clearly supports that application.
Best Use Cases
Structural screws shine in deck ledgers, post caps, beam-to-post connections, stair stringer attachments, and multi-ply beam assembly. They are also useful where wrench access is limited or where a cleaner finish is desired than a through-bolt can provide.
They do not replace every connector. Joist hangers, uplift straps, anchor bolts, and holdowns still rely on specific nails, screws, or bolts approved for that hardware.
Frequently Asked Questions
Can structural screws replace lag bolts?
Often yes, but only when the manufacturer publishes load values and the specific screw has an ICC-ES or equivalent report for that use. Structural screws are not interchangeable with drywall, deck, or multipurpose screws.
Do I need predrilling?
Usually not in standard wood framing, which is one reason structural screws save labor. Large-diameter screws, hardwoods, and tight edge distances may still require pilot holes per the manufacturer installation instructions.
Are structural screws approved for pressure-treated lumber?
Yes, but only if the coating or stainless alloy is listed by the manufacturer for modern copper-based preservatives. Standard zinc finishes are not acceptable.
Related Guides
Choosing the Right Fastener for ACQ Pressure-Treated Lumber
BeginnerCommon Framing Mistakes and How to Avoid Them
IntermediateDeck Framing Best Practices
IntermediateFastener Spacing & Nailing Schedules
IntermediateHow to Build Deck Stairs
IntermediateHow to Frame a Load-Bearing Wall
AdvancedHow to Install a Ledger Board
AdvancedComparisons Featuring This Material
Construction Adhesive vs. Mechanical Fasteners
When to use adhesive, when to use nails/screws, and when to use both. Covers code requirements, strength differences, and best-practice combinations.
Hot-Dipped Galvanized vs. Stainless Steel Fasteners
How to choose between hot-dipped galvanized and stainless steel fasteners for pressure-treated lumber, exterior framing, coastal exposure, and premium decking.
Nails vs. Screws: When to Use Each
A contractor-focused comparison of nails and screws for framing, decking, structural connectors, and finish work. Covers shear, withdrawal, brittleness, speed, and code approval.
Also Consider
Pressure-Treated Lumber
Pressure-treated lumber is dimensional softwood (typically Southern Yellow Pine) infused with preservative chemicals under pressure to resist rot, decay, and insect damage. The most common decking and structural lumber for outdoor applications.
Joist Hangers
Joist hangers are metal connectors that support wood joists, headers, and beams at the end of a member where bearing cannot occur directly over a wall or beam.
Post Bases
Post bases are steel connectors that anchor wood posts to concrete while elevating the post above standing water and transferring compression, uplift, and lateral loads into the foundation.